Absorbent articles such as diapers, training pants, incontinence garments, and the like conventionally include a liquid permeable body-facing liner, a liquid impermeable outer cover, and an absorbent core (also referred to as an absorbent body or absorbent structure) formed separate from the outer cover and liner and disposed therebetween for taking in and retaining liquid (e.g., urine) exuded by the wearer.
Absorbent articles may be designed with extensible or elastic components that improve donning, fit during wear, and removal of the article from the wearer. In some of these absorbent articles, the outer cover and/or the liner may be stretchable to permit some expansion of the article when necessary to provide a better fit on the wearer. For example, a child pulling on a pair of training pants typically pulls both upward on the pants and outward on the pants (e.g., at the waist) to widen the waist opening and pull the pants up over the buttocks and hips to the child's waist. Thus an expansion force is applied to the article to increase the dimensions thereof.
Typically, the absorbent structure of these articles is attached to the outer cover and/or liner to form an attachment zone of the article over which the stretchability of the outer cover and/or liner is inhibited by the less stretchable absorbent structure. The portion of the outer cover and liner that is not attached to the absorbent structure, the non-attachment zone, has a higher amount of stretchability than the attachment zone of the article.
The lateral stretch distribution of the absorbent article is the distribution of stretch across the lateral width of the absorbent article that is needed to expand the waist opening of the article. The distribution of stretch in the circumference of existing articles includes areas with little or no amount of stretch (e.g., the attachment zone) and areas with a relatively higher amount of stretch (e.g., the non-attachment zone) resulting in an uneven lateral stretch distribution in the article. The extension energy of an absorbent article (or a portion of an absorbent article) is defined as the amount of resistance to stretching in the article. The extension energy is inversely proportional to the amount of lateral stretch in the article so that a larger amount of extension energy means that the article will have increased resistance to stretching. An absorbent article having ideal lateral stretch distribution would have an equal lateral stretch distribution and equal extension energy in both the attachment zone and non-attachment zone of the article.
Each layer of material of the absorbent article adds extension energy and resistance to stretching to the outer cover and/or the liner and contributes to the expansion force required to expand the waist opening during donning. The uneven lateral stretch distribution across the circumference of the article requires that the article be made such that substantially all of the stretch needed to increase the circumference of the pant during donning occurs in the portions of the article having a high amount of stretch, typically the non-attachment zone. In existing absorbent articles, the absorbent structure must be reduced in size or made of reduced basis weight in order to reduce the size of the attachment zone, or increase the stretchability of the absorbent structure so as to improve the lateral stretch distribution across the lateral width of the article.
FIG. 32 shows a graph comparing the extension energy of a complete training pant, a stretchable outer cover and liner of the training pant (e.g., without the absorbent structure therebetween), and a stretchable absorbent structure of the training pant. The graph of FIG. 32 illustrates that the complete pant has significantly higher extension energy than both the outer cover and liner and the absorbent structure of the pant. Also, the results indicate that, as expected, the less stretchable absorbent structure contributes a larger amount of extension energy to the entire pant than the outer cover and liner. An ideal training pant design would include an extension energy that is as low as possible to allow elongation of the training pant at a decreased donning force of the article. Further, an ideal pant design would have equal lateral stretch distribution across the attachment zone and the non-attachment zone of the article.
There is a need, therefore, to improve the construction of the absorbent structure of the stretchable absorbent article to decrease the extension energy and the required donning force of the article and to improve the lateral stretch distribution of the article so that the absorbent article may be more easily donned, while maintaining the performance of the article.